Straw choppers on combine harvesters are typically equipped with a rotor having chopper blades suspended in a swinging fashion. The blades rotate at a high speed and enter into clearances defined by stationary counter-blades. The conveyed and chopped material, which may be straw or chaff or a mixture thereof, is conveyed, after being cut through the rotating chopper blades, from the housing of the straw chopper. It then meets with guiding plates disposed downstream from the straw chopper, which deflect the material laterally, allowing it to be distributed across the largest possible part of the cutting width of the combine.
Combine harvesters are presently equipped with ever increasing cutting widths, which make it more and more difficult to spread the material across the cutting width of the combine harvester using such a chopper rotor.
Several suggestions have been made to increase the spreading distance by generating an airflow in that the chopper blades proper are equipped with surfaces for the purpose of creating an airflow that pulls the chopped material with it. The prior art discloses blades attached rigidly to the rotor with plates extending at the rear in the direction of an axis of the rotor (U.S. Pat. No. 3,103,241 A), blades suspended in a swinging fashion (U.S. Pat. No. 3,717,062 A; U.S. Pat. No. 5,232,405 A; and U.S. Pat. No. 5,482,508 A), torqued, swinging blades (U.S. Pat. No. 6,511,374 B), plate-shaped blades extending in the direction of the axis of the rotor and being rigidly connected there (German Patent No. DE 197 49 338 A) as well as U-shaped blades suspended in a swinging fashion including a leg extending in the direction of the axis of the rotor (DE 101 07 776 A) have been suggested. One disadvantage of chopper blades having fan blade surfaces attached thereto or integrated on them (U.S. Pat. No. 3,103,241 A; U.S. Pat. No. 3,717,062 A; U.S. Pat. No. 5,232,405 A; U.S. Pat. No. 5,482,508 A; and DE 101 07 776 A) is that they cannot be inversed after their cutting edges have worn because the surfaces serving the creation of the airflow would come to the leading side, which does not lend itself to a satisfactory cutting behavior. The blades, according to U.S. Pat. No. 6,511,374 B, are expensive to manufacture, and those, according to DE 197 49 338 A, require a high driving power. Therefore it would be desirable to maintain the familiar flat chopper blades and utilize other surfaces for providing airflow.
DE 39 25 701 C describes a straw chopper, where in the space between adjoining chopper blades a fan blade is seated freely pivoting on a fastener that is firmly connected to the chopper shaft. The swinging seat allows a straw guiding flap to be brought into such a position that the chopper is covered during a windrowing operation. However, it also has a disadvantage in that the fan blade, during operation, evades the air pressure and hence has only little effect.
Finally, straw choppers have been equipped with relatively wide fasteners for the chopper blades (U.S. Pat. No. 3,717,062 A, U.S. Pat. No. 6,692,351 B). These may unfold a certain fan blade effect, however they are welded to the rotor and are difficult to replace when they become damaged. Moreover they cannot be disassembled when only a narrow range of the straw chopper is desired for special applications.
What is needed in the art is a combine with a straw chopper, that avoids the aforementioned drawbacks.